Timed cooker



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TIMED COOKER Filed July 8, 1940 10 Sheets-Sheet y 1943- F. w. SCHARF 2,325,551

I TIMED COQKER Filed July 8, 1940 10 Sheets-Sheet 1O tame July 27, 1943 TIMED COOKER Frank W. Scharf, Marshall,

McGraw Electric Company,

poration of Delaware Application July 8, 1940, S erial No. 344,437

27 Claims.

My invention relates to heating devices, and particularly to cookers such as electric automatic toasters, waflle irons, and the like. To insure successful operation heating devices of the types mentioned require timing mechanism which will operate accurately under all conditions of use to establish the proper operating period for the heating means. The first requirement for a timing mechanism for the purpose indicated is that the timing period for operation of the heating means shall be terminated at such time after the beginni g thereof so that the article shall be cooked to a desired degree and neither overcooked nor undercooked; and the timing mechanism should be capable of adjustment so that the cooking period can be regulated arbitrarily to suit individual taste. The second requirement for a timing mechanism for the purpose indicated is that it shall be automatically compensated for varying temperature conditions in the apparatus,

and caused to lengthen or shorten the timing period accordingly, so that uniform results in cooking may be secured under repeated operation, regardless of the temperature at the beginning of each operation of the apparatus as determined by the rapidity with which successive cooking operations are carried out. For example, in the case of an automatic electric toaster the toasting action must continue for a longer time period on the initial slice of bread introduced, when the apparatus is started cold, than in the case of a slice introduced subsequently when as the result of a previous toasting operation the apparatus is relatively hot, and it will generally follow that the toasting time period must be varied in dependency on the rapidity with which successive toasting operations are carried out in order to insure uniformity of results.

According to the present invention the timing mechanism for establishing the time period for cooking operations consists solely of thermostatic mechanism. As one characterizing feature of the invention, thermostatic means i provided which fixe the beginning as well as the end of the time period for the cooking operation. A further characterizing feature of the invention is that in conjunction with thermostatic means for establishing the cooking time period there is provided further thermostatic means responsive to variations in the temperature conditions in the cooking space to lengthen or shorten the cooking period established by the first thermostatic means, thereby to insure the same degree of cooking or browning of successive slices of toast, waffles or other articles.

Mick, assignor to Elgin, 111., a cor- The main timing means according to the invention will comprise thermally responsive means provided with heating means which initially operates to heat the same up from an uncertain or variable cool or low starting temperature to a predetermined higher temperature and then operates to permit the thermostatic means to cool. To secure precision in operation the heating of the thermostatic means to the higher temperature will be carried out, preferably rapidly, as a preliminary operation before the start of the cooking period, and the cooking period will commence only when the thermostatic means has moved to its high temperature position, at which time its cooling period begins; With such an arrangement the cooking period is always initiated when the thermostatic means is at the same predetermined (high) temperature position, and variations in the interval for the thermostatic means to reach its high temperature position from its uncertain cool or low starting temperature has no efiect on the length of the cooking period. The interval required for cooling of the thermostatic means from the predetermined high temperature to which it has been initially heated down to a predetermined cool or relatively low temperature, since it is invariable or constant, provides a very establishing the cooking period.

Normally, the cooking period will be coextensive with the cooling period of the thermostatic means, being commenced when the thermostatic means has been moved by preliminary heating to its predetermined high temperature position and being terminated at the end of the cooling period when the thermostatic means has moved toits predetermined low temperature position. Such an operating arrangement is desirable in that it permits the use of a single thermostatic member which invariably begins and ends the cooking period at fixed temperature positions of the member and sets the length of the cooking period as the time required for it to move from its high to its low temperature position. On the other hand, it is further contemplated according to the invention as an alternative arrangement, as where the form of thermostatic means is such as to have a relatively rapid cooling period, that the thermostatic means shall not upon reaching its cool posi tion render the main heating means inoperative, but upon reaching such position shall set into op... eration control means which will prolong the cooking period and terminate such period at a later time.

It is of course desirable that the cooling period satisfactory time range for a snap action type of thermostatic means which I after preliminary heating from its initial uncertain low temperature position will move to its hot position with a snap action as soon as it reaches a predetermined high temperature and thereupon start cooling. Such means will remain at its high temperature position during its cooling period and will move from such position to its cool position only after it has attained a predetermined low temperature. Utilizing a thermostat operating in such manner enables me to provide a simple form of timing mechanism whereby, at least in the preferred form of the invention, the snap action thermostat will initiate the cooking period as it snaps to its hot position, and terminate the cooking period after cooling as it snaps to its low temperature position.

As previously mentioned the invention further contemplates the provision of a variable control of a thermostatic type which will automatically operate to lengthen or shorten the cooking period, set by the previousl explained heat-up cool-off main uhermostatic means, in accordance with variations in temperature conditions in the cooking or toasting chamber of the apparatus. The variable control means i arranged to delay or hasten the termination of the cooking period preferably, although not necessarily, by acting through the main thermostatic timing means, as by lengthening or shortening the cooling period thereof. For the variable control, I prefer to use a special form of thermostat so located as to be subject to the heat conditions in the cooking chamber. Instead of using a bimetallic or other thermostatic element movable in response to variations in temperature conditions I propose to utilize a thermally responsive electric current conductive device which changes its conductivity with variations in temperature. Such control device can take the form of an electrical resistance element having a high temperature coeficient of electrical resistance 50 as to be sensitive to, and change its electric conductivity with, variations in temperature condition in the cooking space. By incorporating such resistance in the circuit of the control mechanism which serves to terminate the cooking period, I find that an arrangement may be provided which will vary the cooking period in dependency on variations in temperature condition of the cooking chamber with a high degree of accuracy. For example, the electrical resistance element control means may be placed in a circuit with an electric heater operating on the main thermostatic means during its cooling period to lengthen such period, in such arrangement that the hotter the cooking space, and the greater the effective resistance of the resistance element, the less the current that will flow through the heater for the main thermostatic means and consequently the shorter the cooling period of the latter.

The timing mechanism of the invention is particularly useful as an automatic control device for initiatin and terminating operation of the heating means of a cooking apparatus. In such usage the thermostatic timing means will initiate operation of theheating meansat the beginning of the cooling period of the thermostatic means after preliminary heating thereof to its predetermined high temperature, and termination of operation of the heating means will be brought about in dependency on cooling of the thermostatic means to its low temperature position. on the other hand, in some cases, as in a wafile baker where it is ordinarily desirable not to discontinue operation of the heating means between successive bakings,-the timing mechanism of the insignal device, merely to'indicate when cooking of the article should be started and stopped. Again, the timing'mechanism of the invention may per form a duel function of controlling the time period of operation of the heating means of a cooking apparatus, and-of operating signal means which will visually or audibly indicate the cooking period.

. While beingapplicable to various types of cooking devices, or other heating devices wherein the operating period of the heating means must be timed with considerable precision, the invention finds particular utility in connection with automatic electric bread toasters, and will be described in detail in conjunction with a cooking device of such type as illustrated in the accompanying drawings wherein:

Figures 1 through 8 illustrate the preferred embodiment of my timing mechanism employed as a heater control in an automatic electric toaster;

Figure 1 being a vertical front to rear section taken on the line l-l of Figure 8, showing one position of the mechanism;

Figure 2 being a vertical front to rear section taken on the line l-i of Figure 8 showing another operating position of the mechanism;

Figure 3 being a vertical front to rear section taken on the line 3+3 of Figure 8;

Figure 4 being a front elevation of the device;

Figure 5 being a fragmentary section showing an alternate embodiment of the thermostatic timing mechanism;

Figure 6 bein a fragmentary side elevation showing the mechanism in one operating position;

Figure 7 being a fragmentary side elevation showing the mechanism in another operating position; and

Figure 3 being a bottom view of the apparatus;

Figure 9 is a vertical front to rear section of a further embodiment of my thermostatic timing mechanism employed as a control in an automatic toaster;

Figures 10 and 11 are diagrammatic views illustrating the operating circuit ofthe embodiment shown in Figures 1 and 8, and illustrating different operating positions of the parts under different conditions;

Figures 12 through 15 are diagrammatic views illustrating the operating circuits of the embodiment of the invention shown in Figure 9; and

Figure 16' is a diagrammatic view illustrating the use of my timing mechanism in establishing the cooking period of a cooking apparatus through a signal device, and showing the operating circuits in such an arrangement.

Diagram m'ews, Figures 10 and 11 Before describing in full the drawings which illustrate the main embodiment of my invention,

the operating mechanism shown diagrammatically in Figures 10 and 11 will. be described.

In these figures I represents the main heater for the cooker. The heater may be of any desired type, but the preferred form as shown is an electrical resistance heating unit.

I provide a thermally responsive control for the heater consisting oi the bimetallic member 2. Whereas my thermostatic control may utilize thermally responsive members of bimetal or of a simple expanding bar, I prefer the snap action thermostat shown in these figures. As will be observed member 2 is held under resilient compression between supports 3 and II I, and assumes a curved shape.

I provide means for heating the thermostatic control, which, as shown, may'consist of an electrical resistance 4 placed in heat exchange relationship to bimetal member 2.- Resistance 4 may be conveniently wound around the bimetal member 2 being insulated therefrom by suitable material.

I provide control switch 5 which is operated by the thermostatic control member through lever 6. Lever 6 is pivoted at I4 and is actuated by the bimetallic member 2 through the adjustable member I 5. Spring I6 fixed at IT and attached to arm I8 of lever 6 biases the lever to maintain engagement between the bimetal member 2 and adjustable member I5. Arm I9 of lever 6 carries detents 20 and 2| which engage leaf I of switch 5, being insulated therefrom at 22 and 23. It will therefore be apparent that control switch 5 is operated through lever 6 upon movement of the bimetallic member 2.

I also provide main switch 24 consisting of contact 25 carried on spring 26 and contact 21 carried on movable arm 28. Arm 28 is pivoted on pin 29 and is actuated by engagement of pin 32 with the sides of slot 3| in cam plate 30. As will be described later in connection with the specific embodiment of the invention, cam plate 30 is spring biased to a raised position and may be manually lowered to close switch 24 to operate the timed cooker.

For controlling the heat supplied to the thermostatic control, I provide control means for the thermostat heater which operates in dependency on the temperature of the main heater I. This preferably consists of an electrical resistance 33 having a high temperature coefiicient of electrical conductivity and adapted to be heated by the main heater. The change in value of the resistance in dependency on the temperature to which the article to be cooked is subjected is utilized for controlling the cooking period.

I also contemplate the use of my thermally responsive resistance for controlling the timing period of other types of timers known in the art.

If it is desired to provide a manual control for varying the length of the cooking period operating in joint control of the heater with the thermally responsive resistance, a variable resistance may be used to vary the current supplied to the thermostat heater. This may be accomplished by attaching variable resistance 35 operating in series with fixed resistance 34 to posts 36 and 31 in parallel with the thermally responsive resistance 33. 1

Operation A source of electric current for the operation of the heater may be connected to the posts 38 and 39. Conductor 40 leads from post 38 to leaf I of control switch 5. Inits cold position, bi-

metal 2 by arm I9 of lever 6 iorces leaf 1 against leaf 9 to close contacts I0 and II. Conductor 4I leads from leaf 9 of switch 5 to leaf 26 of Switch 24. Conductor 42 connects arm 23 of switch 24 to lead 43 of thermostat heater 4. Conductor 46 connects lead 44 of thermostatic heater 4 to post 39.

Upon lowering of cam plate 30, switch 24 is closed, as is shown in Figure 11. As will be described below, this movement of cam plate III may be accompanied by movement of an article carrier to move the article to be cooked into proximity with main heater I. Latching means, not shown in these figures, are provided for holding cam plate 30, and if desired, the article carrier, in lowered position.

Closing of switch 24, through contacts III and II of switch 5, completes a circuit to thermostat heater 4 from posts 36 and 39. Energization oi. thermostat heater 4 immediately heats bimetal member 2. When the rise in temperature of the bimetal member produced a strain therein sutiicient to overcome the compression 01 supports 3 and III on the member, the same snaps over into the opposite curvature, as shown in Figure 11.

Due to the fact that the full line voltage is applied to the thermostat heater 4, heating up of the bimetal member 2 takes place veryrapidly, and it operates to reverse its position within a very few seconds.

As'is shown in Figure 11, movement of bimetal member 2 upon heating actuates lever 6 to con nect contacts I2 and I3 of switch 5 through the action of detents 20 and 2| on leaf 7. This completes a, circuit for conductor 40 to conductor 46 through switch 5. Conductor 46 leads to main heater I which is connected to post 39 by conductor 41, and consequently the actuation of switch 5 energizes the main heater.

Simultaneously with the connection of contacts I2 and I3, contacts I0 and II are opened to break the circuit from the line to thermostat heater 4. This permits bimetal member 2 to cool. Bimetal member 2 maintains the position shown in Figure 11 until sufllcient strain is set up by the s in temperature to cause it to snap over into the position shown in Figure 10. This operation of the thermostat on becoming cold returns switch '5 to the position shown in Figure 10 and opens contacts I2 and I3 to disconnect the main heater.

The period required for the thermostat to cool constitutes the cooking period during which the main heater is energized. It will be understood that this mode of operation permits an immediate successive operation of the heater by the thermostatic timer, and doesnot require an intermediate period to restore the thermostatic control to an operative condition.

My invention also incorporates means for delaying the cooling of the thermostat in order to produce the desired period of heat treatment. For this purpose, conductor 48 connects lead 43 of the thermostat heater 4, through conductor 42 and switch 24, to post 38 through resistance 33 and conductor 49. The other lead 44, of thermostat heater 4 is connected to post 39 by conductor 45. This circuit is operative to continue energization of thermostat heater 4 after the bimetal member snaps into the hot position shown in Figure 11. Resistance 33 is chosen to have a high value so that the current flowing through thermostat heater 4 permits bimetal member 2 to maintain a continuous fall in temperature, but the heat supplied by resistance 6 is operative to delay the loss of temperature sufllciently to prolong the interval before bimetal member 2 snaps back into cold position as shown in Figure 10.

It is well known that during a succession of timed cooking operations in a device of this character the temperature in the cooking chamber gradually rises. In order to accomplish a diminution in the cooking period for obtaining equal heat treatment despite the variation in temperature during a series of operations, I position resistance 33 so as to be subject to the heat of the main heater in the cooking chamber. It will be understood that as the temperature of resistance '33 rises with the temperature in the cooking chamber its electrical resistance increases. In order to obtain the best control, I use a resistance having a high temperature coefiicient of electrical conductivity. For this purpose the resistance may be composed of iron, or of an alloy of iron and If it is desired to provide a manual control for adjusting the cooking period, this may be accomplished by providing a variable resistance operating to control the current flowing through thermostat heater ll in addition to the control exercised by thermally responsive resistance 33. For this purpose I may attach variable resistance 35 to post 31 and connect in series therewith fixed resistance 34 connected to post 36. Variation of resistance 35 alters the current flowing through heater 1 so that the rate of temperature loss of bimetal member 2 can be varied. I provide fixed resistance 39 in order to prevent shunting of resistance 33 by a resistance of so low a value as to prevent adequate control of the cooking period by the thermally responsive resistance.

As will be described later in connection with the specific embodiment of my invention, I provide means operated by the thermostatic control member on cooling to release cam plate 30 simultaneously with the opening of contacts I2 and I3 of switch 5. At the same time the article carrier which was moved into cooking position by depression of cam plate 30 is released to remove the article cooked from proximity to heater-l.

Therefore, on cooling of the thermostatic control, the entire mechanism is returned to the condition shown in Figure so that the device is immediately capable of performing a successive cooking operation in the manner described.

Figures 1 to 8 In Figures 1 to 8, inclusive, I have illustrated the preferred embodiment in an electric toaster in which the invention diagrammatically shown in Figures 10 and 11 is applied.

In the embodiment shown, provision is made for toasting two slices of bread at a time. The main heater I is composed of four resistances vertically arranged, providing one heating element for each side of each piece of bread. A movable carriage 5| is provided for lowering the bread into the toasting chamber.

As shown in Figure 1, I provide a main base member 52 having supporting legs 53. The base member carries plate 54 on which the mechanism is supported. Base plate 54 carries front plate 55 and rear plate 56, which are attached to the base plate by lugs 51 and 58 respectively. As shown in Figure 4, members 59 and 66 engage the upper edges of plates 55 and 56 and support the upper ends of'the heating elements, as shown in Figure 1. The lower ends of the heating elements are retained in position by lugs 61 and 62.

As shown in Figure 4, vertical guides 63, 64,

.65 and 66 are provided at the front end of the toaster, supported between members 59 and 69 and base plate 54. Guide 63 supports carriage 61 on bearings 6. and guide 66 supports carriage 69 on bearings 18. Carriages 6! and 69 are connected by bar I l. Carriages 6'4 and 89 each support a carrier for receiving the bread and for moving the same into and away from toasting position. As shown in Figure l carriage 69 is provided with rear extensions 12 to which is attached carrier Elymovable vertically in slots 13 and E4 of .end' plates 55 and 56, respectively.

Rods 22! are supported by member 59 and pass through apertures in the bread carrier. These rods prevent bread from coming into immediate contact with the heating elements. Identical structure to that shown in Figure l is provided for the toasting compartment shown on the left of Figure 4.

As shown in Figure 3, I provide lever for actuating carriages 61 and 69. This lever is pivoted on pin 18 carried by rear plate 56 and operates in slot 71' of the rear plate. The forward end of the lever passes through slot 18 in front end plate 55 and engages bar ll connecting carriages 61 and 69 in slot 19.

As shown in Figures3 and 8, arm 89 of lever l5 extends through slot 8! of base plate 59 and is connected to spring 82 which is'adjustably'attachable to the front end of base plate 56 on teeth 83. The action of spring 82 biases carriages 6i and 69 toward the raised position.

The lower end of arm also operates through connecting rod 85' to move piston 85 in cylinder 86 attached at the forward'end of base plate 54. (See Figure 8.) This mechanism acts as a dashpot to efiect gradual movement of carriages 67 and 69 under operation of lever 75. As shown in Figure 4, vertical guides 68 and 65 provide'for movement of carriage 86 on rollers 87. Member 88 is attached to carriage 86 by rivets 89 and 98; and is formed with outwardly projecting handle 96 for operating carriage 86.

At the upper end of carriage 86 is horizontal member 92 engageable with the undersurfaces of members 59 and 69 for limiting the upward. movement of carriage 86 (see Figure 6).

Carriage 86 is provided at its lower end with lateral extensions 93 and 99 engaging carriages 67 and 69 respectively.

It will be understood that movement of carriage 86 by operating handle 9| lowers carriages 61 and 69 to move the bread carrier into cooking position.

As shown inFigures 6 and 7, carriage 61 sup- I ports cam plate 38 on pivot 95. Arm 28'carrying contact 21 of witch 2 3 is provided with pin 32 riding in slot 3|. Pin 32 is insulated from arm 28 :by elements 96 shown in Figure 4. Pin 29 is carried by bracket 91 mounted .on insulating member 98. Insulating member 98 also carries contact 25.

Cam plate 30 is biased by spring 99 which connects pin I09 on plate 30 to pin ill! on carriage 61. Slot I02 in plate 30, through which pin HH passes, allows for movement of plate 39 under tension of spring 99.

As shown in Figure 6,.cam slot 3! is formed so in Figures 6 and 7, latch that when carriage 61 is raised contacts 25 and 21 are open. As carriage 61 is lowered, the upper portion of slot 3| deflects arm 23 by pin 32 to connect contacts 25 and 21. The action of spring 99 provides a resilient pressure for holding switch 24 closed.

I provide means for latching carriages 61 and 69 in their lowered position engageable with extension I03 at the bottom 01' carriage 69. For this purpose I provide bracket I04 carried by the base plate 54. Arm I05 is pivoted to bracket I04 at pin I06, and pressed by spring I08 against stop 222 on bracket I04.

As best shown 'in Figure 6, the lower end of arm I05 carries inclined latch I01. As carriage 69 is lowered by operating handle 9I, latch I01 and arm I05 are deflected by extension I03. As I extension I03 passes below latch I01, spring I08 returns the latch to its original position and holds carrier 69 down as shown in Figure 7. 'As shown at the lower end of arm I05 engaged in slot I26 of latch I01. (See Figure 4.) Spring I21, attached to arm I05 by screw I28 normally presses latch I01 downwardly so that pin I25 engages the upper end of slot I26.. When extension I03 rises against latch I 01; the latch rides up until pin I25 engages the lower end of slot I26.

Latch I01 also carries detent I09 having an in: clined end face IIO. This cooperates with the thermostatic control now to be described to release latch I01 and permit carriages 61 and 69 to be raised through lever 15.

As shown in Figures 1 and 8, a bimetal member 2 is mounted beneath base plate 54. Support 3 of the bimetal member is carried by bracket III mounted on stud I I3.

Bracket II 2 is mounted on stud H4 and at its upper end carries support I I1 of the bimetal member. At its-lower and support II1 is'engaged by link 3' which receivesspring'IH' tensioned by screw II5 on bracket III. Adjustment of screw I I 5, by threaded connector I I6, varies the tension on spring 4' and thereby controls the compression on bimetal member 2. A variation in this compression results in changing the operating temperature required to operate the bimetal member.

Thermostat heater 4 is provided in heat exchange relationship with bimetal member 2, and is provided with leads 43 and 44.

Brackets I I I and H2 are connected by members III! and H9. Member I I9 is provided with upstanding portion I containing slot I2I. Lever 6, pivoted at I4, carries an offset arm I22 working in slot I2 I and overlying bimetal member 2. Arm I 22 is threaded to receive adjustable screw I5 which bears against bimetal member 2. Spring I6 is connected between arm I8 of lever 6 and screw I1 on bracket H2, and causes screw I5 to ride against bimetal member 2 at all times.

As previously described in connection with Figures 10 and 11, arm I9 of lever B operates switch 5.

Arm I9, as shown in Figures 1 and 4, carries pawl I23 biased to the left by spring I24. This pawl cooperates with inclined face IIO of detent I09 of latch I01. As shown in Figure '1, when detent I03 of carriage 69 raises latch I01, extension I09 is raised to be engageable with pawl I23. As arm I9 carries pawl I23 past detent I09 on heating of member 2, inclined face I I0 deflects pawl I23 and doesnot interfere with movement- .of arm I9. On return movement of arm I9 pawl 20 I01 is movably mounted by fixed pin I25 If it is desired to terminate the cooking operation and release carriages 61 and 69 before the end of the timing period, control handle I29 may be manually operated to release detent I03 from latch I01 by drawing arm I 05 outwardly.

As shown in Figure 1, resistance 33 is mounted on rear plate 56 where it i subject; to the heat of the main heater I. Resistance 34 and rheostat 35, which may be optionally employed as described above, are shown mounted beneath base plate 54 in Figure 8. Rheostat 35 adjustment control I30.

Operation of the toaster shown in Figures 1 to 8 After the bread is placed on carrier 5| in the raised position shown in Figure 1, operating handle 9| is lowered to depress carriages 61 and .69 and lower the bread carrier. Latch I01 engages extension I03 of carriage 69 and holds the carriages as well as the bread carrier in cooking position.

As shown in Figure 7, depression of carriage 61 lowers cam plate 30 and brings contacts 25 and 21 together. As described in connection with Figure 10, this energizes thermostat heater 4and produces rapid heating of the bimetal member 2. The bimetal member on being heated snaps over into the position shown in Figure 2 and closes contacts I2 and I3 to energize the main heater I. Through resistance 33, a limited amount of current is supplied to thermostat heater 4 to delay the cooling of bimetal member 2. As described above, the temperature of resistance 33 varies in accordance with the heat supplied to it by the main heater, and it functions to maintain an equalized heat treatment of the bread and compensates for variations in temperature of the toaster which may result from previous cooking operations. Resistance 33 also compensates in some degree for variations in voltage which occurs in some depending on the main line load.

When the temperature of bimetal member 2 has decreased to the operating value, it snaps back into the position shown in Figure 1. By pawl I23 this releases latch I01 and permits carriages 61, 69 and 86 to rise under the action of lever 15 and raises bread carrier 5|. In its" upward passage carriage 61 raises cam plate 30 to open contacts 25 and 21. At the same time movement of arm I9 operates switch 5 to open contacts I2 and I3 and close contacts I0 and II. This deenergizes the main heater and reestablishes the circuit permitting a rapid heating of thermostat heater 4 on subsequent closing of contacts 25 and 21. As described above, the thermostatic time control is immediately available for subsequent operation.

Figure 5 In Figure 5 I have shown another thermostatic time control embodying my invention. This comprises a bimetal warp strip 2a adjustably pivoted on pin I3I carried on bracket IIZa. The bimetal warp strip is held against adjusting screw I32 is provided with localities at various periods vention.

' electric current.

by spring I83 .which is attached to member II8a.

Adjustment of screw I32 is used for varying the operating range of the bimetal warp strip. A heater a for the warp strip is provided as in the previous embodiment. Lever 6a is pivoted on pin Ida and is provided with toggle spring I30 which is anchored on bracket II2a at I00. Arm I221: is provided with adjusting screw I36 having a reduced portion I31 passing through aperture I35 in the warp strip. Stops I38 and III are provided at either end of reduced portion I31 of adjusting screw I36.

The operation of lever 6a under actuation of bimetal warp strip 2a and toggle spring I35 is similar to the operation of lever 6 by the snap action of bimetal member 2. Upon heating, warp strip 2a moves downwardly to engage stop I38, and upon further movement it rotates lever 6a so that toggle spring I05 is carried over dead center to operate switch 6 by arm I8a. As previously described this produces a controlled cooling of bimetal warp strip 2a which begins to rise. When the warp strip comes into contact with stop III it rotates lever 6a in the reverse direction and again causes toggle spring I34 to pass over dead center and return lever 6a to the position shown in Figure 5. i

The cooking period is therefore determined by the time required for the bimetal warp strip to cool and move from its hot position to reset lever 6a. As previously described, this cooling period is subject to control by resistance 33 operating in dependency on the temperature of the main heater.

Diagram views, Figures 12 to In Figures 12 through 15 I have diagrammatically illustrated a second embodiment of my in- These views will be described before explaining the structure in which the second embodiment is incorporated, shown in Figure 9.

As previously described in connection with Figures 10 and 11, the main heater is constituted by electrical heating element I. Thermally responsive resistance 35 is also employed, and is subject to the heat of heater I. I also utilize switch having contacts 25 and 21, and operated by cam slot 31 of cam plate 30.

I provide switch I50 having leaves I5I, I52, I55 and I50. Switch I50 is operated by two thermostatic control members. These control members are preferably snap act ng bimetal strips I8I and I62, as shown. I provide heat supply means for the thermostatic control members, shown as resistanc I63 for bimetal member I6I and resistance I60 for bimetal member I62. Thermostat heater I63 is provided with term nals I65 and I66, and heater I60 is provided with terminals I61 and i86and tap I60.

Bimetal member I61 actuates ball crank lever I69 by adjustable screw I10. Lever I69 is'pivoted at HI and is connected to leaf I53 of switch I50 by insulating link I12. Link I12 extends through aperture I13 in leaf I52.

Lever I14 is operated by bimetal member I62 through adjusting screw I15. Lever I10 is pivoted at I16 and actuates latch I11". Latch I11 is pivoted at I18 and is held by spring I18 against the lower edge of leaf I52.

Terminals I80 and I8I represent a source of Conductor I82 connects terminal I8I to main heater I. Conductor I83 connects main heater I to leaf I5i of switch I50. Conductor I84 connects leaf I52 to terminal I86 of thermostat heater I60. Conductor I85 connects leaf I53 to tap I60. Conductor I81 connects leaf I54 to arm 28 of switch 28. Conductor I88 connects contact 21 of switch 20 to terminal I66 of thermostat heater I63. Conductor I89 connects terminal I66 of thermostat heater I63 to conductor I82. Conductor I connects terminal I80 to terminal I61 of thermostat heater I80. Conductor I5I connects thermally responsive resistance 30 to terminal I50, and conductor I82 connects leaf I50 to the other terminal of resistance 00.

Operation In Figure 9 I have shown the second embodiment of my invention in normal condition. When cam plate 00 is lowered, as previously described, switch 25 is closed to energize thermostat heater I63. Terminal I65 of heater I65is connected to line terminal I8I through conductors I05 and I82. Terminal I85 of heater I60 is connected to line terminal I80 through conductor I50, switch 20, conductor I81, leaf I50, contacts I60 and I58, leaf I58, conductor I85, resistance I00 between tap I 58- and terminal I61, and conductor I90.

Operation of switch I50 by upward movement of bimetal member I6I establishes a limited energization of thermostat heater I58 in the same manner as in the previous embodiment described above. This is accomplished through a circuit including conductor I8I, resistance 33, conductor I92, conductor I81, switch 20, conductor I00, thermostat heater I 65, and conductors I88 and I02. In the same manner as previously described, thermally responsive resistance 33 controls the rate of temperature loss of bimetal member I6I (see Figure 13).

After the desired cooling period during which operation of main heater I is maintained, bimetal member I6I reverses its position and by snap action assumes the curvature shown in Figure 14. This permits leaf I53 to assume an intermediate position, opening contacts I51 and I58. Contacts I55 and I56 are held closed by engagement of latch I11 with leaf I52. The opening of contacts I51 and I58 causes the current flowing through the main heater to pass through the whole of thermostat heater I05. The resulting rise in temperature in bimetal member I62 causes the same after a heating period to assume the curvature shown in Figure 15. This turns lever I10 which comes into engagement with latch I11 and rotates the same to release leaf I52 from notch I93.

Movement of lever I10 operates to release latch I01 as previously described, and permits cam plate 30' to be raised, opening switch 20. Retraction of latch I11 opens contacts I55 and I56 to deenergize main heater I. Leaf I52 returns to its normal position, closing contacts I51 and I58, and I58 and I60.

It will therefore be understood that heating of -metal member I62 must assume the curvature shown in Figure 12 before latch I11 becomes operative again, this is not necessarily before bimetal member I6I goes through its complete cycle of heating and cooling. This will always allow suflicient time for bimetal member I62 t0 cool and permit latch I11 to assume the position shown in Figure 12.

In order to avoid too long a cooking period, in the embodiment shown, I have provided tap I68 on thermostat heater I64, so that this thermostat is preheated by the portion of resistance I64 between tap I68 desired to prolong the heating period for bimetal member I62, tap I68 may be omitted-and conductor I85 connected directly to terminal I61.

In the second embodiment of my invention, therefore, I provide thermostatic time controlled means operative to initiate operation the main heater on being heated, and operative after a cooling period to initiate heating or a second thermostatic time controlled means which is operative after a heating period to terminate operation of the main heater.

Figure 9 mechanisms by the thermostatic time control shown in Figure 9 is identical with that of the thermostatic time controls described above, and is effected through pawl I23 carried by lever I14 which operates on latch I01.

Bimetal member I6I is shown supported on block I94 and flexible member I95. Spring I98 is provided for controlling the compression on bimetal member I6I, and is connected by link I91 to member I95 and by threaded connector I98 to adjusting screw I99. Adjustment of screw I99 varies the compression of bimetal member I6I and controls its operating temperature.

Lever I69 is pivoted to frame 200 by pin HI and is provided with ofiset arm 20I which passes through slot 202 in frame 200 and overlies bimetal member I6I. Adjusting screw I is provided in arm 2IlI for engagement with bimetal member I6I.

Lever I69 is provided with arm 203. Tension spring 204 connects arm 203 to bracket 205 for holding adjusting screw I10 in engagement with bimetal member I6I.

The upper end of lever I69 is provided with aperture 201 through which insulating link I12 attached to leaf I53 of switch I50 passes. Link I I12 is provided with stop 208 with which lever I69 engages to actuate leaf I53.

Bimetal member I62 is supported between block 2I0 and flexible member 209. The compression on bimetal member I62 is controlled by spring 2 connected by link 2I2 to flexibl member 209 and by threaded connector 2 l 3 to adjusting screw 2I4. Variation in the tension of spring 2 by adjusting screwZ I4 is used to control the operating temperature of bimetal member I62.

I provide lever I14 pivoted on pin I16 in frame 2I5 with offset arm 2I6 passing through slot 2I1 of frame 2I5. Arm 2I6 overlies bimetal member I62 and is provided with adjustable screw 2I6 I which bears on bimetal member I62.

Lever I14 is'provided with arm 2I9. Tension spring 22I connects arm 2I9 to bracket 205 for holding adjusting screw 2I8 in contact with 'bimetal member I62.

At the upper end of bracket 205 I provide arm and terminal I61. In case it is,

m which'sup'ports pin m on which latch m is rotatably mounted. Spring I19 connects latch I11 to bracket 205 and normally biases latch I11 -into contact with leaf I62."

. a signal device.

- will be understood nals At the upper end of lever I14 is provided pin 220 engageable with latch I11 to rotate the same against the action of of lever: I14 caused her I62.

Lever I14 also carries pawl ing spring I24. As described previously, pawl J I23 operates on latch I01 to release carriages 61 and 69 which raise the bread carrier and, through cam plate 30, open contacts 25 and-21. The' operation of the mechanism shown in Figure 9 description of Figures 12 through 15.

- Signaldevice operated by thermostatic timer In Figure 161' have shown diagrammatically my thermostatic timer in a circuit for operating spring I19 upon movement Main heater 226, as shown, comprises electrical resistance elements connected to line termi- 38 and 89 by conductors 228 and 229 respectively. Switch 221 is provided in conductor 229 for controlling operation of the main heater.

I provide signal lamp 222 for indicating the cooking period. The thermostatic timer shown in Figure 16 for operating signal lamp 222 is in all respects similar to that shown in Figures 10 and 11, with the exception that the signal lamp is substituted in the circuit for main heater I, and switch 225 is substituted for cam operated It will be understood that the thermallyresponsive resistance 33 is adapted to be heated by main heater 226' and function as previously described.

The operation of the mechanism shown in Figure 16 is particularly adapted for use in a Waiiie iron or similar cooker where it is customary to maintain continuous operation of the main heater. This is accomplished by closing switch 221. Signal lamp 222 is utilized for indicating the desired cooking period. The operation of the timer isinitiated by closing of switch 225. As from the previous description, this produces a rapid heating of the bimetal member which, upon moving to its heated position, energizes lamp 222 and indicates the beginning of the cooking period. During the cooling of the thermostat, lamp 222 is maintained in operation until the bimetal member moves to its cold position and terminates operation of the lamp to indicate the end of the cooking period.

Variable resistance 35 may be used for select ing the desired cooking interval for the material to be treated.

- The thermostatic timer in Figure 16 is adapted to operate continuously to indicate a series of successive cooking intervals. This is accomtion the actuation of switch 5 causes a quick heating-of the bimetal member again, so that a successive timing cycle follows each cooling of the thermostat.

If it is desired to terminate the operation of by heating of'bimetal memm and its actuatwill be understood by reference to the the thermostatic timer after one operation, switch 24 and its thermostatically controlled actuating means may be substituted for switch 225 so that upon movement of the thermostatic member to its cold position the circuit is broken and the timer does not operate in.a succeeding cycle. It will be understood that the circuit as shown in Figure 16 operates to indicate aseries of successive cooking intervals until switch 225 is opened. Operation oi the cooker is terminated by opening switch 221 to deenergize main heater 226, as well as switch 225 to terminate operation of the thermostatic timer.

I claim:

1. In a bread toasting device, a heater, a toasting space heated by the heater, timing means determining the toasting period of the heater comprising thermally responsive means becoming operative upon movement by heating to a a predetermined temperature to initiate operation of said heater to raise the temperature of the space and start the toasting period, and means for terminating operation of said heater to lower the temperature of the space and end the toasting period operating in dependency on cooling of the thermally responsive means to a predetermined lower temperature.

2. In a bread toasting device, a toasting space, a primary heater for heating the space to toasting temperature, and'timing means determining the toasting period of the heater comprising a thermally responsive element adapted to be heated during a period preliminary to operation of the primary heater and having a following cooling period, auxiliary heating means for heating the thermally responsive element during its preliminary period, and control means for establishing timed intervals of toasting operation of the primary heater responsive to the thermally responsive element at the beginning of its cooling period to initiate toasting operation of the primary heater and start the toasting period in said space and being adapted as a result of cooling of the thermally responsive element to render the primary heater inoperative and discontinue the toasting period in said space.

3. In a heating device, a primary heater, thermostatic control means for establishing timed operating intervals for the primary heater operative on heating to initiate operation of the heater and operative on cooling to terminate operation of the heater, means for heating the thermostatic control means controlled by said thermostatic control means, and means for decreasing the cooling rate of the said thermostatic control means in such a manner as to increase the timed interval of operation of the said primary heater.

4. In a heating device, a primary heater, thermostatic control means for establishing timed intervals of operation of the primary heater the said thermostatic control means adapted as the result of preliminary heating to initiate operation of the heater and the said thermostatic control means adapted as the result of a cooling period to terminate operation of the heater, means for preliminarily heating the thermostatic control means, and variable control means controlled by said thermostatic means and said primary heater for decreasing the cooling rate of the said thermostatic control means'in such a manner as to increase the timed interval of operation of the said primary heater.

5. In a heating device, a primary heater, thermostatic control means for establishing timed intervals of operation of the primary heater,

the said thermostatic control means adapted as the result of being preliminarily heated to initiate operation of the heater and the said thermostatic control means adapted as the result of a cooling period to terminate operation of the heater, and variable heating means adapted to preliminarily heat thethermostatic control means rapidly and becoming operative in dependency on heating of the thermostatic control means to supply heat at a reduced rate to control the cooling rate of the thermostatic control means.

6. In a heating device, a primary heater, thermostatic control means for establishing timed intervals of operation of the primary heater operative to initiate operation of the heater and the said thermostatic control means adapted as the result of a cooling period to terminate operation of the heater, variable heat supply means adapted to preliminarily heat the thermostatic control ineans and operable thereafter to control the cooling period of the thermostatic control I position to a predetermined lower temperature position, electrical heating means initially operative to supply heat sufficient to move the thermally responsive element to its high temperature position and operable during cooling of the element to control the rate of cooling, means for supplying operating electric current to said electrical heating means operable to supply less current thereto during the cooling period than during the heating period of the thermally responsive element, and means operating in dependency on cooling movement of the element to its lower temperature position for setting the time for I terminating operation'of the primary heater.

8. In a heating device, aprimary heater, and mechanism for timing operation of the primary heater including a thermally responsive element initially movable by heating to a, predetermined high temperature position and then cooling and movable reversely from said high temperature position to a predetermined lower temperature position, electrical heating means for heating the thermally responsive element operative during the heating periodof the element, and also operative during the cooling period of the element to control its rate of cooling, means for supplying current to the heating means during the. heating period of the element sufiicient to cause the heating means to move the element to its high temperature position, said supply means being rendered inoperative by the thermally responsive element upon reaching its high temperature position, further current supply means including electrical resistance means for supplying current in less amount to the heating means during the cooling period of the thermally responsive ele ment, said further current supply means being rendered operative by the thermally responsive element upon reaching its high temperature position, and means operating in dependency on cooling movement of the element to its lower temperature position for setting the time for terminating operation of the primary heater.

9. In a bread toasting device, a toasting space, a primary heater for heating the space to toasting temperature, and timing mechanism for determining the toasting period of the heater comprising thermostatic control means for the heater including a bowed bimetallic member operative upon preliminary heating to assume the opposite bowed curvature by snap action and thereupon initiate operation of heater and start the toasting period in said space, auxiliary heating means for preliminarily heating the bimetallic member and control means for said last mentioned means operative to terminate said preliminary heating on snap action by the bowed metallic member;

10. In a bread toasting device, a toasting space, a primary heater for heating the space to toasting temperature, and timing mechanism determining the toasting period of the heater comprising thermostatic control means for the heater including a bowed bimetallic member operative upon preliminary heating to assume the opposite bowed curvature by snap action and thereupon initiate operation of the primary heater and start the toasting period in said space, and said bimetallic member being operative thereafter upon cooling to return to its initial bowed curvature by snap action and thereupon render the primary heater inoperative and end the toasting period in said space, means for preliminarily heating the bimetallic member and control means for said last mentioned means operative to terminate said preliminary heating on snap action by the bowed metallic member from its initial to its opposite bowed curvature.

11. In a bread toasting device, a toasting space, a primary heater for heating the space to toasting temperature, thermostatic control means for establishing intervals of time action of the primary heater operative upon heating to initiate operation of the heater, means for preliminarily heating the thermostatic control means, means operating in dependency on cooling of the thermostatic control means for terminating operation of the primary heater, and variable control means operating in dependency on the primary heater for delaying the rate of cooling of the thermostatic control means,

12. In a bread toasting device, a toasting space, a primary heater for heating the space to toasting temperature, thermostatic control means operative to control toasting operation of the heater, electrical heating means adapted to supply heat at a variable rate to the thermostatic control means, and control means for said electrical heating means operating in dependency on the temperature of the primary heater to vary the rate of application of heat by said electrical heating means to the thermostatic control means.

13. In a heating device, a primary heater, a thermally responsive element initially movable by heating to initiate operation of the primary heater and reversely movable on cooling, means operating in dependency on cooling movement of the thermally responsive element for terminating operation of the primary heater, electrical heating means for the thermally responsive elementoperating during its cooling period to control the rate of cooling, and control means for said electrical heater means comprising a thermally variable electrical resistance device subject to the heat of the primary heater and operating to control the heat imparted by the electrical heater means to the thermally responsive element in accordance with the temperature of the primary heater.

the primary the temperature of pendency on cooling of said 14. In a cooking device, aheater and a cooking chamber adapted to be raised to cooking temperature by said heater, and timing mechanism for establishing the cooking period for the article to be cooked by the heater including a thermally responsive element becoming operative, upon heating to a predetermined temperature to initiate'operation of the heater and start the cool:- ing period in the chamber, and means for terminating operation of the heater and ending the cooking period in the chamber operating in deelement to a predetermined lower temperature. 15. In a cooking device, a heater and a cooking operative to control the length of the cooling period of the thermally responsive element.

18. In a bread toaster,

19. In an automatic toaster, a heater, a toasting space heated by the heater, a bread carrier movable to and from toasting position in the thermally responsive toasting space, a thermally responsive element, heating means rendered operative by the bread carrier upon movement to toasting position to heat the thermally responsive element to a predetermined high temperature, means operative upon said element reaching its predetermined high temperature to start said element cooling from its predetermined high temperature to a predetermined lower temperature, means responsive to heating of the thermally responsive element to its predetermined high temperature to initiate operation of the main heater, and means responsive to cooling of the thermally responsive element to its predetermined lower temperature to terminate operation of the main heater and effect movement of the bread carrier away from toasting position in the toasting space.

20. In a bread toaster according to claim 18, thermally responsive means operating in dependency on the main heater to adjust the temperature of the auxiliary heating means and control the temperature of the thermally responsive element during its cooling period.

21. In a heating device, a heater, power supply means for energizing said heater, electrically controlled timing means for terminating operation of the heater, electrical circuit means independent of the power supply means for the heater for controlling the timing means, and heat responsive electrical resistance means in said electrical circuit means operating in dependency on the temperature of the heater to control operation of the timing means.

22. In a heating device, a heater, power supply means for energizing said heater, electrically controlled timing means for terminating operation of the heater, and electrical circuit means for controlling the timing means including heat responsive electrical resistance means operative to supply an E. M. F. to the timing means varying inversely with the temperature of the main heater.

23. In a cooking device, a cooking chamber, means for raising the temperature of said chamber, timing mechanism controlling'the operating said means including a thermally reelement operative upon heating to a period of sponsive predetermined temperature to initiate operation of said means and to raise the temperature of the chamber.

24. In a timer, a thermally responsive element, electrical heating means operative to heat said element to move the same to a predetermined high temperature position, and then allowing the element to cool to a predetermined low temperature position, said electrical heating means operating upon the thermally responsive element during its cooling period to control duration of the cooling period, a timing control member, means for actuating the timing control member operating in dependency on movement of the thermally responsive element to its high temperature position at the end of its heating period, and means for actuating the timing control member operating in dependency on movement of the thermally responsive element to its low'temperature position at the end of its cooling period, and thermostatic control means responsive to varying temperature conditions other than the temperature conditions of the thermally responsive element controlling operation of the heating means acting on the thermally responsive element during its cooling period.

25. In a timer, a thermally responsive element, electrical heating means operative to heat said element to move the same to a predetermined high temperature position, arid then allowing the element to cool to a predetermined low temperature position, said electrical heating means operating upon the thermally responsive element during its cooling period to control duration of the cooling period, a timing control member, means for actuating the timing control member operating in dependency on movement of the thermally responsive element to its high temperature position at the end of its heating period, and means for actuating the timing control member operating in dependency on movement of the thermally responsive element to its low temperature position at the end of its cooling period, and thermostatic control means responsive to varying temperature conditions other than the temperature conditions'of the thermally responsive element to vary the cooling period of the thermally responsive element, the same comprising an electrical resistance element varying its electrical conductivity in response to variations in temperature and being located in a circuit with the electrical heating means operating during the cooling period of the thermally responsive element to control the heat produced by said means.

26. An automatic toaster comprising toast heating elements, a bread carrier movable to and from toasting position relatively to said heating elements and biased to non-toasting position, a latch to hold the carrier in toasting position, a bimetal bar, an electric heater therefor, a switch means for controlling said heating elements and said electric heater, said switch means upon movement of said carrier to toasting position and without energizing the toast heating elements being efiective to cause energizetion of said heater and heating of the bimetal bar to a predetermined high temperature position, said bar upon reaching said high temperature position actuating said switch means to cause partial deenergization of said electric .heater and energization of said heating elements,-

said bimetal bar then cooling from its predetermined high temperature to a predetermined lower temperature and effective at said predetermined lower temperature to cause release of said latch with return of the carrier to non-toasting position and actuate the switch means to cause deenergization of said toast heating elements.

27. In a bread toasting device, a toasting space, a primary heater for heating the space to toasting temperature, and timing means determining the toasting period of the heater comprising a primary thermostatic control means therefor adapted as the result of heating to a predetermined temperature to initiate operation of the heater and start the toasting period in said space, means adapted as the resultof cooling of the said primary thermostatic control means to a lower temperature to terminate operation of the heater and end the toasting period in said space, and auxiliary control means for delaying termination thermostatic control means.

FRANK- W. SCI-IARF. 

